Effects of incense on brain function: evaluation using electroencephalograms and event-related potentials

To evaluate the effect of the odor of incense on brain activity, electroencephalograms (EEGs) and event-related potentials (ERPs) in a push/wait paradigm were recorded in 10 healthy adults (aged 23-39 years) with normal olfactory function. EEG was recorded from 21 electrodes on the scalp, according to the International 10-20 system, and EEG power spectra were calculated by fast Fourier transform for 3 min before and during odor presentation. ERPs were recorded from 15 electrodes on the scalp before, during and after exposure to incense with intervals of 10 min. In a push/wait paradigm, two Japanese words, 'push' as the go stimulus and 'wait' as the no-go stimulus, appeared randomly on a CRT screen with equal probability. The subjects were instructed to push a button whenever the 'push' signal appeared. Fast alpha activity (10-13 Hz) increased significantly in bilateral posterior regions during incense exposure compared to that during rose oil exposure. The peak amplitudes of no-go P3 at Fz and Cz were significantly greater during incense inhalation. The latencies of go P3 and no-go P3, and the amplitude and latencies of no-go N2 did not change by exposure to the odors of both incense, rose and odorless air. These results suggest that the odor of incense may enhance cortical activities and the function of inhibitory processing of motor response.